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In
HVAC terms, Malcolm Rowe may have the coolest home in Putnam County,
N.Y. Rowe recently constructed a 5,800-square-foot residence boasting
an immaculate energy envelope. The home, finished in July 2011,
has gained recognition as an Energy Star Version 2.0 Home Energy
Rating System Index 47 labeled home, certification as a U.S. Environmental
Protection Agency (EPA) Indoor AirPLUS labeled residence, and is
pending LEED for Homes Silver accreditation.
Rowe’s construction objective was to achieve ultimate thermal
comfort and superior air quality. To achieve this goal, he enlisted
the services of Walden, N.Y.-based Radiant Technology LLC contractor
Aaron Ourada.
In assessing the situation, Ourada prioritized comfort at the top,
followed closely by sustainability and energy efficiency. He achieved
these goals by installing hydronic heating and cooling systems,
filtered whole-house ventilation, and automated humidity controls.
“If you want the most comfortable and efficient home possible,
you have to start by studying our planetary home, the Earth,”
he said. “How is the Earth heated and cooled? Next study how
the human body gains and loses heat. It’s surprising how simple
and elegant an HVAC system can be when we copy the master.”
Sustainable Installation
After learning about energy efficiency incentives through New York
State Energy Research and Development Authority’s (NYSERDA)
Energy Star Labeled Homes program, Rowe approached Norwalk, Conn.-based
Steven Winter Associates Inc. (SWA) for guidance.
SWA officials determined his home improvement goals aligned with
the LEED for Homes program through material and resource efficiency,
sustainable sites, water efficiency, and IAQ.
Integral to sustainable design, the home’s efficient thermal
envelope includes R26 insulated concrete forms (ICFs) below grade
on an R10 slab. R26 ICFs continue above grade to the framed R54
roof sprayed with 3 inches of closed cell and 6 inches of open cell
insulation. A thermal imager was used to verify insulation, and
to identify weaknesses in the envelope for repair.
The home’s efficiency is furthered through water-to-water
GeoComfort ground-source heat pumps by Enertech Manufacturing for
radiant floor heating and an Uponor radiant cooling system. The
heat pumps are fitted with a desuperheater, which reclaims energy
for domestic hot water storage and dehumidification reheat.
A RenewAire EV450IN ERV provides whole-house ventilation and central
bathroom exhaust. A Unico System M Series high-velocity air-handling
unit maintains whole-house humidity control through a MERV 10 filter,
ECM motor, chilled water coil, heating coil in reheat position,
and connected Nortec humidifier.
Triangle Tube’s 95 percent efficient condensing boiler is
included as a heating backup with domestic hot-water production
provided by Triangle Tube’s smart indirect-fired water heater.
The domestic well utilizes an energy-efficient and constant-pressure
variable-speed submersible pump made by Grundfos. The water and
geothermal vertical wells were drilled by Boyd Artesian Well Co.
of Carmel, N.Y. A low-emitting Renaissance Rumford wood-burning
fireplace features a fully sealed, gasketed door and ducted combustion
air.
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Energy-Efficient
Operation
To optimize energy efficiency, the hydronic circulators used in
conjunction with the ground-source heat pumps provide heating and
cooling by pulse width modulation duty cycle and variable speed
control.
The first four circulators are 15-58FC zone pumps, operating on
medium speed at 60-80 W with a 50 percent duty cycle for December
through February, and July through August; and a 25 percent duty
cycle for other months. The next circulator is also a 15-58FC pump
that is controlled as a variable-speed injection pump operating
at a 20-60 W maximum.
Another circulator is boiler heat backup, 15-58FC, on medium speed
at 80 W, only running about 20 percent duty cycle January through
February. A final pump, 26-99FC, operates on medium speed 179 W
and is for direct-coupled ground-source radiant cooling only operating
in the summer at 50 percent duty cycle. This combination heat pump
flow control uses about 480 W to heat and cool the structure.
Rowe’s home also features in-floor radiant heating and cooling.
The system is embedded in concrete for each floor, as the basement
is slab on grade, and the second and third floors are poured concrete
over ICF decking. The concrete thermal mass construction acts as
a thermal energy flywheel to offset overnight peak loads, so the
mass stores energy and regulates temperature fluctuations.
“Bill Cotton, of Cotton’s Concrete in Athens, Pennsylvania,
and his team had to work very closely with Aaron on the installation
of the tubing into the LiteDeck floor slabs,” said Rowe. “It
was a pleasure working with some great contractors who I knew I
could trust, and they did not let me down.”
The home’s swimming pool is also a key component, acting as
another geothermal heating/cooling source. When the heat pump is
operating for air conditioning, and the pool is in heating mode,
controls divert the energy normally transferred from the home to
the Earth, instead from the home to the pool. Geothermal heat exchange
efficiency is somewhat less going to 80¾F pool water rather than
55¾F ground; however, the compromise is beneficial as the pool heating
becomes a byproduct of air conditioning.
When the pool heat is off, controls divert back to using the vertical
ground loops as needed for air conditioning. This design required
a properly sized close approach flat plate heat exchanger made of
titanium to endure the saltwater pool treatment system.
For radiant cooling, the ground-source heat pump system reverses
from heating mode to cooling, charging the 120-gallon buffer tank
with chilled water instead of hot water. A variable-speed mixing
pump controls the water temperature from the buffer tank to the
radiant floor cooling system.
The ERV provides 253 cfm intermittently (11 hours/day) to meet ASHRAE
Standard 62.2.
With sensible recovery efficiency of 67 percent and total-recovery
efficiency of 46 percent, the energy recovery ventilator is in line
with most equipment efficiencies, but uses a significant 490 W during
run time; fortunately, it also doubles as a bathroom local exhaust.
The home is monitored and controlled via an Automated Logic building
automation system, which can access all 16 zones through remote
sensors that are Internet accessible.
“Aaron has a rare passion for technology and all things involving
HVAC,” said Rowe. “He guided me through our joint vision
for a highly energy-efficient house comprising a geothermal energy
source, radiant heating and cooling, insulating spray foam, and
web-enabled monitoring and control systems. I had to trust him,
and it paid off.” |
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